Geography · 15 Oct 2026

Budhi Gandaki Gandak river system

Consider the following statements:

  1. The Budhi Gandaki rises near the Manaslu massif and joins the Trishuli river.
  2. The Trishuli joins the Kali Gandaki to form the Narayani.
  3. The Narayani enters India as the Gandak and meets the Ganga in Uttar Pradesh.
  4. The Chamoli disaster of February 2021 was triggered by the breach of a glacial lake.
AOnly one
BOnly two
COnly three
DAll four
This question is based on: The Flood That Begins Beyond the Map: A Nepal Debris Flow and India's Upstream Blind Spot
Take this in full test mode → Instructions for 15 Oct 2026
About this question

Why in news

On 11 October 2026, a debris-laden flash flood struck the Budhi Gandaki in Gorkha, Nepal. The river gauge at Arughat peaked at 8.43 metres. The flood exposed a gap: India has no early warning for hazards that begin upstream, across the border, on rivers that later reach India.

Why for UPSC

UPSC often tests river systems through how tributaries join and where a river meets the main stream. It also tests whether aspirants can tell apart the triggers of disasters like Kedarnath (a lake breach) and Chamoli (an avalanche).

Prelims summary

The river sequence is Budhi Gandaki → Trishuli → (joins Kali Gandaki) → Narayani → Gandak in India → Ganga in Bihar. The Kedarnath flood of 2013 came from the Chorabari lake breaking. The Chamoli flood of 2021 had no lake: it was a rock-and-ice avalanche. Both were debris flows, where loose sediment does the damage.

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